Electric signal transfer systems

ABSTRACT

A rotary kiln has a number of thermocouples respectively sensing the kiln temperature at spaced locations and respectively connected to annular slip rings each in kiln sections. Laterally facing peripheral surfaces of the rings are respectively cooperable with brush contacts connected to a bar and a fork which embraces a ring moveable axially with the rings. Thus, on longitudinal expansion of the kiln the contacts are caused to move with the rings. The electric signal from the thermocouples are fed to a stationary sensor. In a modification the ring sections are electrically isolated and each section is connected to a respective sensor. Position sensors may be used to detect the rotary position of the kiln. The invention can be applied to other sensors.

This invention relates to an electric signal transfer systems fortransferring electric signals from a rotary kiln to a stationaryreceptor for the signals.

A rotary kiln may be used for gas/liquid/solid counter or co-currentreactions. A rotary kiln assembly usually comprises an inletarrangement, a rotary kiln, and an outlet arrangement, it beingunderstood that product materials can be fed into or extracted fromeither the inlet arrangement or the outlet arrangement. Sealarrangements are provided between the rotary kiln and the inletarrangement and the outlet arrangement.

Rotary kiln assemblies may operate within a large temperature rangeextending from room temperature to several hundred degrees Celsius. Thismeans that allowance must be made for differential thermal expansion ofthe rotary kiln relative to the inlet and the outlet arrangements.Excessive heating of the rotary kiln must also be prevented to protectproduct materials inside the rotary kiln, and materials used in theconstruction of the rotary kiln.

One problem presented by relatively long rotary kilns is that oftransferring electric signals, for example from sensing devices on therotary kiln, to a stationary receptor such as a control system.

According to the invention a rotary kiln has a plurality of sensingmeans thereon, and an electric transfer system for transferring electricsignals from the sensing means to a stationary receptor, the transfersystem comprising a plurality of co-axial, electrically conducting,substantially annular members, a respective electrically conductivecontact member for each annular member arranged to contact a laterallyfacing peripheral surface of the respective annular member, the annularmembers and the contact members being arranged such that rotation of therotary kiln causes relative rotation between the annular members and thecontact members, and means for causing longitudinal displacement of thecontact members corresponding to any longitudinal displacement of theannular members.

Preferably, the annular members are mounted co-axially on the rotarykiln and are electrically connected to the sensing means, the contactmembers being electrically connectable to the receptor. Resilient meansmay be provided to bias the contact members towards the respectiveannular members.

The displacement means may comprise a ring member co-axial with andlongitudinally displaceable with the annular members, a translationalmember upon which the contact members are mounted and extending parallelto the axis of the rotary kiln, and a guide member mounted on thetranslational member, the guide member being located about the ringmember so as to cause translational movement of the translational membercorresponding to any longitudinal displacement of the ring member.

Desirably, the guide member is biased towards one axial side of the ringmember, and comprises a fork member having tines about the ring member.Each annular member may comprise a plurality of segments arranged in aslight eccentric relationship to each other to produce correspondingslight radial displacement of the contact members during said relativerotation. Desirably, the eccentric relationship of the segments in suchas to produce radial inward displacement of the respective contactmember during said relative rotation in a selected direction.

In one arrangement transfer of the electrical signals from the sensingmeans to the stationary receptor is effected through the agency of anumber of sets of part-annular members such that, during each revolutionof the rotary member, each contact member successively engages eachpart-annular member of a respective set, said part-annular members beingelectrically isolated from each other and being electrically connectedto respective sensing means.

In this way, during each revolution, electrical continuity is effectedbetween each contact member and the sensors to which the correspondingpart-annular members are connected and consequently each contact memberserves to transfer a plurality of signals per revolution.

Preferably means for detecting at least one predetermined angularposition of the rotary kiln relative to a datum position or positionswhereby the output signals obtained from each contact member can berelated to the part-annular members (and hence the sensors) from whichsaid outputs are derived.

The sensing means may comprise temperature sensing members. The sensingmembers may be disposed on the rotary kiln such that some of the sensingmembers provide electric signals related to the temperature of regionsinside the rotary kiln, and some of said sensing members provideelectric signals related to the temperature of the rotary kiln.

The invention may be performed in various ways and some specificembodiments will now be further described by way of example only withreference to the accompanying diagrammatic drawings, in which:

FIG. 1 is a side elevation of a rotary kiln assembly;

FIG. 2 is a side elevation of a slip ring or sensing assembly;

FIG. 3 is an axial view of a slip ring and contact assembly on lineIII--III of FIG. 2;

FIG. 4 is a side view of part of a slip ring assembly on the line IV--IVof FIG. 3;

FIG. 4A is a view on line A--A of FIG. 4;

FIG. 5 is a part side view of a kiln;

FIG. 6 is an axial view of FIG. 5 on the line VI--VI;

FIG. 7 shows a thermocouple mounting;

FIG. 8 illustrates electrical connections to thermocouples.

FIG. 9 is a side view of part of a slip ring assembly corresponding tothat shown in FIG. 4 with the addition of proximity detectors;

FIG. 10 is a block diagram of circuitry for correlating the outputs ofthe contact members with the respective sets of sensors.

FIG. 11 is a modification of FIG. 8; and

FIG. 12 is a modification of FIG. 3.

Referring now to FIG. 1, a rotary kiln assembly 10 comprises an inletarrangement 11, a rotary kiln 12, and an outlet arrangement 13. Theinlet arrangement 11 includes a solid material feed inlet 14, and theoutlet arrangement 13 includes a material outlet 15. The rotary kiln 12includes a number of temperature controllable sections or zones 17heated by respective exterior heater sections or zones 18 (not shown inFIGS. 4 to 7) and cooled by convection coolers (not shown), so that adesired axial and transverse temperature profile can be obtained withinthe rotary kiln 12.

Seal arrangements 19 and 20 are disposed between the rotary kiln 12 andthe inlet arrangement 11 and the outlet arrangement 13 respectively. Therotary kiln assembly 10 is supported on concrete supports 21, 22, withthe rotary kiln 12 being carried by respective roller mountings 24, 25on the supports 21, 22, the mounting 24 also retaining the rotary kiln12 axially to allow thermal expansion of the rotary kiln 12 to occurover the roller mounting 25. An electric powered drive assembly 23disposed on the support 21 is arranged to rotate the rotary kiln 12.

The rotary kiln assembly 10 operates in a temperature range extendingfrom ambient temperatures to hundreds of degrees Celsuis, so thatallowance has to be made for thermal expansion of components of, orwithin, the rotary kiln 12. The rotary kiln 12 might expand (direction BFIGS. 1 and 4) of the order of 10 cm towards the outlet arrangement 13and therefore the seal arrangement 20 must allow for relative axialmovement of the rotary kiln 12. Careful control of the temperatures ofthe sections 17 is important to protect product materials inside therotary kiln 12, and also the materials used in the construction of therotary kiln 12 itself. This requires effective temperature monitoringand assessment so that remedial action can be taken promptly, thetemperature monitoring being provided by thermocouples 30 (see FIGS. 5and 7) disposed at selected positions along the rotary kiln 12. Thethermocouples 30 enable a clear picture of the kiln surface temperatureprofile along the rotary kiln 12 to be deduced from the electric signalsfrom the thermocouples 30, by locating a thermocouple 30 axiallycentrally in each section 17 adjacent to outer surface of the kiln andradially inwards of the heaters 18. A thermocouple 30a is also disposednear each end of each section 17 adjacent the outer surface of the kilnto provide electric signals used for switching off the respectiveheaters 18 in the event of an excessive temperature of the rotary kiln12 being detected. The heaters 18 are also switched off by failure ofany one of the end thermocouples 30a of any of sections 17, or by faultytransmission or processing of the signals from the end thermocouples30a. Leads from the thermocouples 30, 30a are provided with a loop 31(see FIG. 5) in each lead before the lead is fed into a housing orchannelling 32 on the rotary kiln 12. The housing 32 guides and protectsthe thermocouple leads from the position where they emerge from therotary kiln 12 to a region 26 within the circle A of FIG. 1. The loops31 are provided so that differential thermal expansion of the rotarykiln 12 and a thermocouple lead can be compensated for by flexing of therespective loop 31. Another spare set of thermocouples 30, 30a for eachsection is provided on the opposite side of the kiln (see FIG. 6) sothat if a thermocouple fails the corresponding spare thermocouple may beconnected to reduce machine down time.

The thermocouples 30, 30a (including the spares) connect to fourterminal blocks 40 (see FIGS. 4 and 7) the negative side of all thethermocouples 30 being common to one point 70 in the terminal blocks 40,and the positive side of the thermocouples 30, 30a being fed to separateterminals in the blocks 40 via multistrand wiring 71. Single strandwiring in the thermocouple sheath is shown at 72. Each thermocouple 30positive side from the three sections 17 is connected from the block toa separate copper-coated mild steel slip ring 34 (see FIGS. 3 and 8) andthe common negative side is fed to a single slip ring 34a. The positivesides of the thermocouples 30a in the three sections 17 are connectedrespectively to further slip rings 34 and the negative sides of thethermocouples 30a are connected to another single slip ring 34a. Thethermocouple spares are only connected to the slip rings when required.A cold pot seal 41 connects the major thermocouple wiring 72 to flexiblewires 71 for connection into the terminal block 40. The seals 41 areheld in a frame 42 secured to the kiln 12 and to which the terminalblock 40 is secured.

From the terminal block 40, wiring to each slip ring 34, 34a isduplicated by being connected in parallel to both of the major slip ringsections, as mentioned later. The slip rings 34, 34a are carried onangularly spaced axial metal plates 44 (FIG. 4) with suitable insulatingmaterial sheets 35a being interposed to ensure that the slip ringsignals cannot short together, the plates 44 being supported on brackets45 which are in turn bolted to the kiln 12 via bolts 48 (FIGS. 3 and 4).The thermocouple terminal blocks 40 are supported on the frames 42 (seeFIG. 4). The slip rings 34, 34a are co-axial, electrically conductingand substantially annular. The rings 34, 34a are electrically insulatedfrom each other by insulating brushes 35 which receive bolts (not shown)which hold the rings to the sheets 35a and plates 44.

From FIG. 3 it can be seen that electrical signals from the slip rings34, 34a are collected by respective electrically conductive contactmembers in the form of brushgear arrangements 50, each brush comprisinga holder 51 carrying a pair of carbon brushes 52 loaded by a spring 53so as to engage the outer peripheral face 34b of the respective slipring, and electrically connected in parallel to provide redundancy. Eachholder 51 is mounted on a translational member or bar 55, located on acarrier 56 (not shown in FIG. 4) and which is traversable in a directionB FIG. 4 longitudinally of the rotary kiln 12 relative to a fixed table57. This allows for axial expansion and contraction movement of therotary kiln 12 relative to its fixed end at the roller mounting 24. Themovement of the bar 55 relative to the table 57 is controlled by atraversing ring 58 on the kiln 12 of larger diameter than the rings 34,34a and disposed at the heater 18 side of the collection of rings 34,34a (FIG. 2). The traversing ring 58 locates between the tines 59 of aguide member or fork 60 (FIG. 4) at one end of the bar 55. Leads (notshown) from the brushes 52 are connected to monitoring equipment (to bedescribed with reference to FIG. 8 below), which provides a temperatureprofile display and can serve to actuate control equipment forcountering any temperature reading which is considered to be outside atolerance range. The fork 60 may be biased such as by having a weightdependent therefrom as shown schematically at 60a in FIG. 4, so that thefork 60 is always in abutment with one side of the traversing ring 58,thereby ensuring that movement of the traversing ring 58 is accuratelytransmitted to the bar 55.

The slip rings 34, 34a are split into three segments indicated by aminor segment 69, and two major segments 67, 68 in FIG. 3, for ease ofassembling on the kiln and to permit ready access. The segments 67, 68,69 are also arranged such that during rotation of the kiln 12 in aselected direction C FIG. 3, the brushes 52 move radially downwardly ona step 66 (shown exaggerated) between the segments 67 and 68 and betweenthe segments 68 and 69 and between segments 69 and 67. This ensures thatthe brushes 52 are not subjected to undue breakage forces when passingover a joint between the segments 67, 68, 69. The step may for examplebe 0.16 cm. Further, the rings 34, 34a are arranged to be slightlyeccentric, so that radial movement of the brushes 52 and theirassociated springs 53 is assured during operation to stop the brushes 52becoming set in one position.

Reference is now directed to FIG. 8, from which an outline of plantoperation can be deduced and in which like reference numerals inpreceding Figures are used for like parts. In FIG. 8, the centralthermocouple 30, being the temperature controlling thermocouple, and theend thermocouples 30a, being the shutdown thermocouples as aforesaid,the negative leads of all the thermocouples 30 (only one section shownin FIG. 8) are commoned by a line 70. The line 70 feeds to the negativeinput of measuring devices 81, 81a, one device being provided for eachof the thermocouples 30, 30a. In order to inhibit common mode failures,an opto-isolator 82 is arranged between the line 70 and the device 81,81a in each case. The positive side of each thermocouple 30, 30a is fedto the positive input of a respective one of the devices 81, 81a. InFIG. 8, the slip rings 34, 34a are shown diagrammatically. Outputs fromthe devices 81, 81a are fed to a plant monitoring apparatus 80. Outputsfrom devices 81a go to over-temperature protection devices 83 whichreduce or cut off the supply to the heaters 18 when an over-temperatureis sensed, and devices 81 are connected to a temperature control device84 which adjusts or cuts off the supply to the heaters 18 to maintainthe sensed temperature in a desired range or at a desired value. Thesemonitoring features are deemed within the knowledge of the skilled manand are shown schematically.

It is to be understood that fewer or additional thermocouples may beprovided depending on the application. For example, in the rotary kiln12 a thermocouple 30b (see FIG. 1) may be located inside the kilnlongitudinally centrally along the length thereof, to monitor thetemperature of the product being treated in the rotary kiln 12, thisadditional thermocouple having its positive side connected to a separateslip ring 34 but having its negative side connected to the same slipring 34a as that used by the common negatives from the centralthermocouples 30 of FIG. 5. Hence spare slip rings 34 may be provided toallow additional thermocouples to be fitted during use of the rotarykiln assembly.

In FIG. 2 twelve slip rings 34, 34a are shown, which allows a slip ring34 for each thermocouple 30, 30a (i.e. nine) and two slip rings 34a usedas common slip rings respectively by the central thermocouples 30 andthe end thermocouples 30a, (a total of eleven slip rings). The spareslip ring 34 may be used with an aforesaid additional thermocoupleinside the rotary kiln 12, or for some other application. On someoccasions, further thermocouples might be provided inside the rotarykiln 12 near the ends, these thermocouples being located in cantileveredmetal tubes extending into the rotary kiln 12, so that leads from suchthermocouples may be connected to control equipment without beingtransmitted through the slip rings 34, 34a and the associated brushes.

With reference to FIGS. 9 to 12, which provide a more compact signaltransfer system, as described above, each slip ring 34, 34a isfabricated from three part-annular segments which are electricallyconnected together. In accordance with the modified arrangement, thesegments forming each slip ring 34 (but not slip rings 34a) areelectrically isolated from one another by omitting electrical braidingor such like interconnecting them and by introducing electricallyinsulating inserts 90 FIG. 12 (e.g. PTFE inserts) between the adjacentends of the segments. In addition, instead of a single sensor (e.g.thermocouple) being connected to a slip ring, according to themodification a different sensor is connected to each segment of eachslip ring so that each slip ring 34 is coupled to three sensors (FIG.11). Such an arrangement enables the number of slip rings 34 to bereduced considerably. As before, one pole (e.g. negative side) of eachsensor may be connected to the common slip ring 34a.

Although in the embodiment described above, each slip ring 34 is dividedinto three segments, a greater or lesser number of segments per slipring may be employed with a corresponding number of sensors coupled toeach set of segments. The segments of each ring are so arranged that thegaps therebetween are all substantially aligned axially with thecorresponding gaps between the segments of all of the other sets.

To facilitate discrimination between the segments in each set andthereby correlate the outputs of each brushgear arrangement 51, 52,means is provided for furnishing signals indicative of the position ofthe kiln. Such means may comprise, for example, suitably arrangedinductive-type proximity sensors 100, 102 and targets or markers 104,106. Thus, for example, the sensors 100 and 102 are mounted onstationary structure and the targets are rotable with the kiln. In onearrangement, one set of axially aligned segments may be associated withtwo targets 104 and 106; a second set of axially aligned segments may beassociated with only a target 104; and the third set of axially alignedsegments may be associated with only a target 106. In this way, theoutputs of sensors 100, 102 can be used to indicate which segments aretraversing the brushgear arrangements 51, 52 at any instant. The targets104, 106 may be peripherally co-extensive with the segments they areassociated with or they may be somewhat shorter in peripheral extent.

Referring now to the diagrammatic circuit of FIG. 10, this illustratesrouting of the thermocouple signals from one segmented slip ring to amultichannel recorder 108. The thermocouple signals, after collection bythe respective brush gear 50, are processed (e.g. amplified) by signalconditioning circuit 110 and applied to a number of sample and holdcircuits 112a-c whose outputs are connected to different channel inputsof the recorder 108. The circuits 112a-c are controlled by respectiveENABLE signals applied via lines 114 by logic circuitry 116 which, inturn, serves to analyse the outputs of proximity sensors 100, 102 andthereby determine which particular segment of the slip ring (and hencewhich thermocouple) is engaged by the brush gear 50. Thus if, forexample, proximity sensors 100, 102 both provide outputs indicative ofthe presence of both targets 104 and 106, circuit 112a may be enabled toreceive the thermocouple signal and transfer it to recorder 108. If onlytarget 104 is detected, circuit 112b may be enabled and, likewise, ifonly target 106 is detected, circuit 112c may be enabled.

In a more sophisticated circuit arrangement, a microprocessor may beutilised in such a way that, during the time the brush gear is engagedwith each segment, the thermocouple signal is repeatedly sampled toderive for example an average value which is then fed to themultichannel recorder.

Although the invention has been described in relation to transmittingelectric signals from thermocouples, other electric signals may betransmitted, for example from a plurality of strain gauges attached to arotary member.

We claim:
 1. A rotary kiln having a plurality of sensing means thereon, and an electric transfer system for transferring electric signals from the sensing means to a stationary receptor, the transfer system comprising a plurality of co-axial, electrically conducting, substantially annular members, a respective electrically conductive contact member for each annular member arranged to contact a laterally facing peripheral surface of the respective annular member, the annular members and the contact members being arranged such that rotation of the rotary kiln causes relative rotation between the annular members and the contact members, and means for causing longitudinal displacement of the contact members corresponding to any longitudinal displacement of the annular members, said displacement means comprising a ring member co-axial with and longitudinally displaceable with the annular members, a translational member upon which the contact members are mounted and extending parallel to the axis of the rotary kiln, and a guide member mounted on the translational member, the guide member being located about the ring member so as to cause translational movement of the translational member corresponding to any longitudinal displacement of the ring member.
 2. A rotary kiln as claimed in claim 1, in which the annular members are mounted co-axially on the rotary kiln and are electrically connected to the sensing means, the contact members being electrically connectable to the receptor.
 3. A rotary kiln as claimed in claim 1 including resilient means arranged to bias the contact members radially towards the respective annular members.
 4. A rotary kiln as claimed in claim 1, including means biassing the guide member towards one axial side of the ring member, the guide member comprising a fork member having tines about the ring member.
 5. A rotary kiln as claimed in claim 1, in which each annular member comprises a plurality of segments arranged in slight eccentric relationship to each other to produce corresponding slight radial displacement of the contact members during said relative rotation.
 6. A rotary kiln as claimed in claim 5, in which the eccentric relationship of the segments is such as to produce radial inward displacement of the respective contact member during said relative rotation in a selected direction.
 7. A rotary kiln as claimed in claim 1 in which the sensing means comprises temperature sensing members.
 8. A rotary kiln as claimed in claim 7, in which the sensing members are disposed on the rotary kiln such that some of the sensing members provide electric signals related to the temperature of regions inside the rotary kiln, and some of said sensing members provide electric signals related to the temperature of the rotary kiln.
 9. A rotary kiln having a plurality of sensing means thereon, and an electric transfer system for transferring electric signals from the sensing means to a stationary receptor, the transfer system comprising a plurality of coaxial, electrically conducting, substantially annular members, a respective electrically conductive contact member for each annular member arranged to contact a laterally facing peripheral surface of the respective annular member, the annular members and the contact members being arranged such that rotation of the rotary kiln causes relative rotation between the annular members and the contact members, means for causing longitudinal displacement of the contact members corresponding to any longitudinal displacement of the annular members, transfer of the electrical signals from the sensing means to the stationary receptor being effected through the agency of a number of sets of part-annular members such that, during each revolution of the rotary kiln, each contact member successively engages each part-annular member of a respective set, said part-annular members being electrically isolated from each other and being electrically connected to respective sensing means, and means for detecting at least one predetermined angular position of the rotary kiln relative to a datum position or positions whereby the output signals obtained from each contact member can be related to the part-annular members (and hence the sensors) from which said outputs are derived.
 10. A rotary kiln as claimed in claim 9 in which the annular members are mounted co-axially on the rotary kiln and are electrically connected to the sensing means, the contact members being electrically connectable to the receptor.
 11. A rotary kiln as claimed in claim 9 including resilient means arranged to bias the contact members radially toward the respective annular members.
 12. A rotary kiln as claimed in claim 9 in which each annular member comprises a plurality of segments arranged in slight eccentric relationship to each other to produce corresponding slight radial displacement of the contact members during said relative rotation.
 13. A rotary kiln as claimed in claim 12 in which the eccentric relationship of the segments is such as to produce radial inward displacement of the respective contact member during said relative rotation in a selected direction.
 14. A rotary kiln as claimed in claim 9 in which the sensing means comprises temperature sensing members.
 15. A rotary kiln as claimed in claim 14 in which the sensing members are disposed on the rotary kiln such that some of the sensing members provide electric signals related to the temperature of regions inside the rotary kiln, and some of said sensing members provide electric signals related to the temperature of the rotary kiln. 